This invention relates to detection of xe2x80x9cmarkxe2x80x9d and xe2x80x9cspacexe2x80x9d widths in an incoming digital signal stream.
When a digital signal stream is being received, the temporal width of each mark values (high states or xe2x80x9c1xe2x80x9d) and the temporal width of each space value (low state or xe2x80x9c0xe2x80x9d) can vary within an acceptable range, or may sometimes have a width outside the acceptable range, such as w1xe2x89xa6wxe2x89xa6w2. Where a mark width or a space width lies within the corresponding acceptable range, a digital signal processing device can recognize and properly process that mark or space. However, a mark width (or space width) that is too large or too small, and thus lies outside an acceptable range, must be promptly detected.
What is needed is a system and method for examining a stream of digital signal marks and spaces sequentially and for quickly recognizing a mark or a space (referred to as a digital signal stream xe2x80x9ccomponentxe2x80x9d) that has a width w that is smaller than a first value w1, or that is greater than a second value w2, and for promptly associating an indicium with this component that indicates that the width of this component lies outside the corresponding acceptable range.
These needs are met by the invention, which provides a system and method for off-line examination of mark widths and space widths and for association of a selected indicium with every stream component having a width w that lies outside a permissible range, such as w1xe2x89xa6wxe2x89xa6w2. This examination process requires only a small, constant time delay, related to the relative sizes of the width values w1 and w2, so that processing of the resulting (compensated) digital signal occurs uninterrupted, apart from this small, constant time delay. The digital signal stream is divided into groups of consecutive marks and consecutive spaces, and each group of consecutive marks or consecutive spaces is examined in turn. This allows the width examination process within each group to proceed without requiring separate and time-consuming identification of each incoming signal component as a mark or a space.